Merge fix-apt-preferences-hides-upgrades [f=1374338] [r=tealeg,ack] [a=Free Ekanayaka]
This branch:
- makes the client clear the hash->id requests table when resynchronizing,
which was not done before because of possible pending messages delivering
that request to a different server. Now that we have session IDs those
outgoing messages will be discarded, so there's no need for the trick.
- adds a missing test that fails if one removes the "not version.package.is_upgradable"
clause of the if statement in facade.py line line 422.